Atherosclerosis has been known to be an important disease in humans since the beginning of recorded medical history. However, it was not until the early portion of the twentieth century that it became clearly recognized that the syndrome of myocardial infarction was associated with coronary atherosclerosis and thrombosis. Epidemiological studies during the 1970's demonstrated that cardiovascular disease is the cause of approximately 50% of all deaths in western civilization. Recent observations suggest that there has been a decline in mortality from coronary heart disease associated with a reduction in the incidence of coronary atherosclerosis. Despite the apparent reduction in mortality from coronary heart disease, atherosclerosis remains an important cause of death in the United States.
Since the late 1970's, coronary balloon angioplasty has become an accepted form of therapy for coronary artery disease. Unfortunately, in about a third of patients undergoing this treatment, intimal hyperplasia occurs and vascular restenosis appears within about six months after surgery. Proliferation of smooth muscle cells in the walls of blood vessels treated by balloon angioplasty followed by restenosis of the blood vessel is recognized as a serious drawback of balloon angioplasty. In addition to restenosis of blood vessels after balloon angioplasty, smooth muscle cell proliferation leading to stenosis of blood vessels is also a serious drawback of percutaneous transluminal coronary angioplasty and is associated with accelerated coronary atherosclerosis after cardiac transplantation. Consequently, there is a great need for agents and treatments to reduce smooth muscle cell proliferation found in blood vessels after these types of surgical procedures.
Antistasin is a protein found in salivary gland extracts of the Mexican leech Haementeria officinalis having antimetastatic and anticoagulant activity. Tuszynski et al. (1987) J. Biol. Chem. 262: 9718-9723 report isolation and characterization of antistasin from the salivary glands of the Mexican leech Haementeria officinalis. Nutt et al. (1988) J. Biol. Chem. 263: 10162-10167 report the amino acid sequence of antistasin. Antistasin possesses 119 amino acid residues and is blocked at its amino terminus by the presence of a pyroglutamic acid residue and has an unusually high cysteine content, with 20 cysteine residues. The primary structure of antistasin shows no homology to hirudin, a 65-residue anticoagulant protein from the medicinal leech, Hirudo medicinalis. Antistasin contains significant internal homology where a 2-fold internal repeated structure is observed. At least four isoforms of antistasin have been identified in leech salivary gland extracts by high performance liquid chromatography, and partial amino acid sequence or analysis of these isoforms indicates they differ by one or two amino acid residues.
U.S. Pat. No. 4,588,587 issued May 13, 1986 to Gasic discloses a method for treating a patient to inhibit metastasis of malignant cells by administering to a patient a therapeutically effective amount of a leech salivary gland extract. The patent also discloses a method for preparing the salivary gland extract.
Gasic et al (1983) Cancer Research 43: 1633-1636 reports the inhibition of lung tumor colonization by leech salivary gland extracts.
Bajowski et al (1984) Proceeding of the American Association for Cancer Research 25: 58, abstract 230 reports the inhibition of murine tumor cathepsin B by leech salivary gland extracts from Haementeria officinalis.
Gasic et al. (1984) Cancer Research 44: 5670-5676 reports inhibition of cyclophosphamide- and radiation-induced artificial metastasis enhancement by an extract of the salivary glands from Haementeria officinalis.
Gasic et al. "Inhibition of metastasis and cytotoxic agent-induced metastasis enhancement by leech salivary gland extracts" in Treatment of metastasis: Problems and prospects PROCEEDINGS, Hellman and Eccles, eds, Taylor and Francis, London and Philadelphia, 1985, pp. 275-278, reports the inhibition of metastasis formation and prevention of enhancement of metastases induced by iatrogenic agents by an extract from the salivary glands of the leech Haementeria officinalis.
Tick anticoagulant peptide (TAP) is a sixty amino acid protein isolated from the tick Ornithodoris moubata which is a highly specific inhibitor of blood coagulation factor Xa, Waxman et al. (1990) Science 240: 593-596. Tick anticoagulant peptide contains six cysteine residues, and exhibits limited homology to the Kunitz class of inhibitor. Tick anticoagulant peptide exhibits a high degree of specificity for factor Xa, and is reported to have no effect on Factor VIIa, kallikrein, trypsin, chymotrypsin, thrombin, or several other factors in the blood coagulation cascade, (Waxman et al., supra).